This invention relates to an electrical test connector designed to be connected to the wiring harness of a motor vehicle's speed control system in order to perform a diagnostic check of a plurality of electronic sensors and functions.
More particularly, this invention relates to a method by which an electrical test connector may be used for diagnostic checking of the 1973 and later FORD Speed Control System components with or without the FORD Resume function.
As it is perhaps well known, many motor vehicles on the road today are factory equipped with a speed control system commonly known as "cruise control", which allows the driver to automatically regulate the speed of the vehicle by the use of a control head on or near the steering column. These speed control systems work on a variety of electromechanical and electronic mechanisms which are peculiar to the make and model of the vehicle, but in all cases the said systems require maintenance and diagnostic checking to insure that the system is working properly.
FORD'S first speed control system appeared in 1960 and was replaced in 1973 and revised in 1979 to their current Speed Control System with Resume feature as an option in all their car lines, except Taurus and Sable, and it is the same system in many thousands of FORD vehicles on the road today. The 1979 FORD Speed Control System with Resume feature (hereinafter referred to and the "FORD System") is operated by controls on the vehicle steering wheel which in turn is connected to various system components and sensors through the speed control amplifier. In normal operation this speed control amplifier serves as an interfacing circuit between the driver's controls and the vehicle sensors and, as such, it determines the throttle setting by voltage inputs from the control switches, vehicle speed and throttle plate position. The speed control amplifier contains two wiring harnesses: input and output, each comprising six circuits. The input circuits have been designated by FORD by wire color as follows: Ignition Feed Circuit (purple); Amplifier Control Line Circuit (light blue-black hash); Brake Feed Switch (light green); Vehicle Sensor Ground to Sensor Signal (black); Sensor Signal (dark green-white stripe); Servo Vacuum Solenoid (gray-black hash). Accordingly, the output circuits have been designated by FORD by wire color as follows: Servo Power/Servo Vent/Servo Vacuum Solenoid (gray-black hash); Servo Vent Solenoid (white-pink hash); Servo Feedback/Negative/Servo Feedback Position (purple-light green hash); Servo Feedback Position (yellow-red hash); Servo Feedback/Positive (brown-light green hash); Amplifier Ground (black).
Now that the aforesaid circuits have been identified in the FORD System, a background discussion of the current diagnostic procedures shall be briefly explained. Heretofore, only two methods could be used to test the said FORD System. The first method is by use of the Rotunda Speed Control Tester No. 007-00013, manufactured by Bendix. This is a sophisticated and computerized multi-system diagnostic tester which is relatively expensive and difficult to operate for the average automobile repairman. Needless to say, it is found in only the most complete automobile repair shops and, therefore, it is rarely used. The second method is the manual method which consists of disconnecting the wiring harnesses at the amplifier and then checking each circuit connector with a voltmeter/ohmmeter. This is the method commonly in use, however to use this method it is necessary to first locate the correctly colored wire entering the harness and then insert the probes of the voltmeter/ohmmeter on the corresponding connectors. Accordingly, it can be easily seen that this task is somewhat like looking for a needle in a haystack, especially in a vehicle where the wires have become dirty or discolored with time as is usually the case. For example, it should not be too difficult to imagine looking for the difference between a purple wire and a purple wire with light green hash with a flashlight under a dashboard. Even if the colors could be distinguished, there is the additional problem of trying to read the voltmeter/ohmmeter.
It has long been felt that an alternative means was necessary for the average automobile repairman to perform diagnostic testing of the FORD System with accuracy, simplicity, and ease of operation. The above objective among others is achieved by using a specially designed electrical test connector, in conjunction with the herein described method, for diagnostic checking of the FORD System.